U.S. patent application number 09/909789 was filed with the patent office on 2003-01-23 for temperature-controlled charcoal grill and method therefor.
Invention is credited to Harbin, Lawrence.
Application Number | 20030015188 09/909789 |
Document ID | / |
Family ID | 25427834 |
Filed Date | 2003-01-23 |
United States Patent
Application |
20030015188 |
Kind Code |
A1 |
Harbin, Lawrence |
January 23, 2003 |
Temperature-controlled charcoal grill and method therefor
Abstract
A temperature-controlled charcoal barbecue grill comprises a
housing, a charcoal-fired chamber, a cooking region, a cover or lid
substantially enclosing the cooking region and charcoal-fired
chamber, and a temperature control module that controls temperature
in the cooking region using either a mechanical shutter to control
radiant energy exposure or an arrangement of fans to displace or
circulate air. Preferably, the grill includes a power converter
that converts heat to electrical energy to power the control module
and associated accessories such as a series of vent fans that
supply and exhaust the cooking region, a charcoal blower fan to
help oxidize burning charcoal, and an internal circulation fan to
help maintain an even temperature distribution within the cooking
region. Audible and visual indicators may also indicate various
predetermined conditions during operation and control cycles of the
grill. Corresponding methods of control are also disclosed.
Inventors: |
Harbin, Lawrence;
(Alexandria, VA) |
Correspondence
Address: |
LAWRENCE HARBIN
2906 MAPLEWOOD PLACE
ALEXANDRIA
VA
22302
US
|
Family ID: |
25427834 |
Appl. No.: |
09/909789 |
Filed: |
July 23, 2001 |
Current U.S.
Class: |
126/25R ;
126/21A; 126/21R |
Current CPC
Class: |
A47J 37/0718 20130101;
A47J 37/0786 20130101; A47J 37/0754 20130101 |
Class at
Publication: |
126/25.00R ;
126/21.00R; 126/21.00A |
International
Class: |
A47J 037/00; F24B
003/00 |
Claims
I claim:
1. A temperature-controlled charcoal barbecue grill comprising: a
housing; a charcoal-fired chamber; a cooking region; a cover that
substantially encloses the cooking region and the charcoal-fired
chamber with the housing; and a controller responsive to a setpoint
and a sensor to control heat in the cooking region by controlling
one of airflow with the cooking region and radiant energy from the
charcoal-fired chamber that reaches the cooking region.
2. The charcoal barbecue grill as recited in claim 1, wherein the
amount heat is controlled by controlling an air path in
communication with at least one the charcoal-fired chamber and the
cooking region.
3. The charcoal barbecue grill as recited in claim 1, wherein the
controller includes an adjustable shutter to control the amount of
energy radiated from the charcoal-fired chamber that reaches the
cooking region.
4. The charcoal barbecue grill as recited in claim 2, wherein the
sensor is selected from a group including a thermocouple,
bimetallic element, a temperature probe, an infrared sensor, and a
heat sensor, and wherein the sensor detects temperature of one said
cooking region and said charcoal-fired chamber.
5. The charcoal barbecue grill as recited in claim 4, further
comprising a converter the converts heat emitted from said
charcoal-fired chamber to electricity in order to power said
controller.
6. The charcoal barbecue grill as recited in claim 5, wherein said
converter comprises a thermoelectric converter.
7. The charcoal barbecue grill as recited in claim 2, wherein the
controller activates a blower fan that directs air directly upon
the charcoal-fired chamber in order to control burn rate of fuel
therein.
8. The charcoal barbecue grill as recited in claim 3, wherein the
adjustable shutter is adjustable by action of a bimetallic element
in order to control temperature in said cooking region.
9. The charcoal barbecue grill as recited in claim 2, wherein said
controller comprises a microprocessor.
10. The charcoal barbecue grill as recited in claim 9, further
comprising a thermo-electric generator the converts heat energy
emitted from the firebox to a useful current that powers the
microprocessor.
11. The charcoal barbecue grill as recited in claim 1, further
comprising an electrically activated indicator that indicates one
of cooking temperature and output energy of the charcoal-fired
chamber.
12. The charcoal barbecue grill as recited in claim 11, wherein the
indicator comprises at least one of an LED and audible tone
generator.
13. A temperature-controlled charcoal barbecue grill comprising: a
housing; a charcoal-fired chamber; a cooking region; a cover that
substantially encloses the cooking region and the charcoal-fired
chamber with the housing; a sensor that senses at least one of
temperature of the cooking region and energy radiated from the
charcoal-fired chamber; a source of power derived from said
charcoal-fired chamber; and a microprocessor controller responsive
to a sensor to control temperature in the cooking region by
controlling a flow of air communicating with at least one of the
cooking region and the charcoal-fired chamber, the microprocessor
controller being powered by said source of power.
14. The temperature-controlled barbecue grill as recited in claim
11, wherein said source of power comprises a thermoelectric
converter the converts waste heat from the charcoal-fired chamber
to electricity.
15. The temperature-controlled barbecue grill as recited in claim
13, further including at least one blower powered by said source of
power to establish said flow of air.
16. The temperature-controlled barbecue grill as recited in claim
13, wherein said source of power comprises a steam-driven
mechanism.
17. The temperature-controlled barbecue grill as recited in claim
13, further comprising an electrically activated indicator that
indicates one of cooking temperature and output energy of the
charcoal-fired chamber, said indicator comprising at least one of
an LED and audible tone generator.
18. A method of controlling cooking temperature in a charcoal
barbecue grill comprising: providing a charcoal-fired chamber and a
cooking region; substantially enclosing the cooking region and
charcoal-fired chamber within the housing; sensing at least one of
temperature of the cooking region and energy radiated from the
charcoal-fired chamber; deriving power from heat produced by the
charcoal-fired chamber; and using the power to control temperature
of the cooking region by producing a flow of air communicating with
at least one of the cooking region and the charcoal-fired chamber
according to a preset temperature.
19. The method as recited in claim 18, further comprising
indicating attainment of a preset temperature of said cooking
region.
20. The method as recited in claim 18, further comprising
indicating attainment of a preset energy output of said
charcoal-fired chamber.
21. A method of controlling cooking temperature in a charcoal
barbecue grill comprising: providing a charcoal-fired chamber and a
cooking region; substantially enclosing the cooking region and
charcoal-fired chamber within a housing; sensing at least one of
temperature of the cooking region and energy radiated from the
charcoal-fired chamber; and using sensed heat to control
temperature of the cooking region by at least one of controlling a
vent and energy radiated from the charcoal-fired chamber reaching
the cooking region.
22. The method as recited in claim 21, further comprising providing
a bimetallic element to sense heat produced by the charcoal-fired
chamber.
23. The method as recited in claim 22, further comprising actuating
a shutter using the bimetallic element in order to control radiant
energy reaching the cooking region.
Description
BACKGROUND
[0001] The present invention relates to charcoal barbecue grills,
but more specifically, to controlling cooking temperature in a
charcoal or wood-burning grill.
[0002] Unlike gas-fired and electric grills, controlling internal
cooking temperatures of charcoal or wood-fired grills is difficult
or requires complicated mechanisms. Temperature control is desired
to permit constant-temperature baking or roasting, to reduce food
charring, or to minimize the amount of time required to attend
cooking. Due to a chimney effect achieved with vertical hearth
grills, briquettes burn hotter, steady, and more efficiently, thus
outputting extreme amounts of heat. Thus, it is desired to provide
a way to control excess heat and reduce charring of meats. In
conventional charcoal grills, temperature control was achieved by
regulating air vents in the firebox, but this was often ineffective
in view of other factors affecting charcoal burn rates, such as
grease and liquid runoffs. Such runoffs frequently extinguished the
coals or flamed-up, thus adversely impacting internal
temperatures.
[0003] U.S. Pat. No. 6,230,700 to Daniels, et al. addresses
internal temperature control by providing air circulation within a
cooking chamber to disperse heat evenly within its cooking region,
but does not adequately control internal cooking temperature in
accordance with a temperature feedback sensor/detector or
adjustment of amount of heat emanating from the heat source.
[0004] In view of the deficiencies of prior charcoal-fired barbecue
grills, a feature of the present invention provides control of
internal cooking temperature or radiant energy exposure by
controlling ingress and/or egress of air with a cooking region
and/or by controlling the amount of radiant or convection heat from
the firebox that reaches the cooking region. This and other
features are achieved electronically and mechanically.
SUMMARY OF THE INVENTION
[0005] In accordance with one aspect of the present invention, a
temperature-controlled charcoal or wood-burning barbecue grill
comprises a housing, a charcoal-fired chamber, a cooking region, a
cover or lid that engages the housing to substantially enclose the
cooking region and charcoal-fired chamber with the housing, and a
temperature control module that controls the amount of heat
supplied to the cooking region. In one particular embodiment, the
charcoal grill additionally includes a power converter that
converts heat to electrical energy in order to power the control
module and associated accessories that may include a series of
controllable vent fans that supply and exhaust the cooking region,
a controllable charcoal blower fan to help oxidize burning
charcoal, and an internal circulatory fan to help maintain an even
temperature distribution within the cooking region. Audible and
visual indicators may also be included to indicate various
predetermined conditions during the operation and control cycles of
the grill.
[0006] In accordance with another aspect of the present invention,
a method of controlling cooking temperature in a charcoal-burning
barbecue grill comprises providing a charcoal-fired chamber and a
cooking region, substantially enclosing the cooking region and
charcoal-fired chamber within the housing, sensing at least one of
temperature of the cooking region and energy radiated from the
charcoal-fired chamber, deriving power from said charcoal-fired
chamber, and using power derived from said charcoal-fired chamber
to control the amount of heat of the cooking region either by
mechanically adjusting a shutter to control the amount of energy
reaching the cooking region or by generating a flow of air
communicating with the cooking region or the charcoal-fired
chamber. Electrical power may be derived from a thermoelectric
power converter while mechanical power may be derived in a variety
of ways including use of a bimetallic actuator or other
thermo-mechanical device.
[0007] Other features and aspects of the invention will become
apparent upon review of the following disclosure taken in
conjunction with the accompanying drawings. The invention, though,
is pointed out with particularity by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 shows a side view of a vertical hearth barbecue grill
in which aspects of the invention may be deployed.
[0009] FIGS. 2A and 2B show perspective and side views of an
enclosed cooking region of the vertical hearth barbecue grill of
FIG. 1, and further depict a series of microprocessor controllable
venting fans in accordance with one aspect of the present
invention
[0010] FIGS. 3A and 3B show front and rear perspective views of a
control module depicted in FIGS. 2A and 2B, which module embodies
control electronics, sensors, and indicators in accordance with an
aspect of the present invention.
[0011] FIG. 4 is a functional block diagram of a circuit for
implementing temperature control functions according to one
embodiment of the present invention.
[0012] FIG. 5 is a flow chart depicting one method of performing
temperature control functions according to one embodiment of the
present invention.
[0013] FIG. 6 is a flow chart depicting another method of
performing temperature control functions according to another
embodiment of the present invention.
[0014] FIG. 7 depicts a mechanically controllable shutter and
control mechanism used in conjunction with a vertical firebox
hearth of a vertical barbecue grill for maintaining temperature
control according to yet another embodiment of the present
invention.
[0015] FIG. 8 shows deployment of a temperature control module on a
cover or lid of the barbecue grill depicted in FIG. 1.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0016] According to the invention, temperature in a cooking region
of a charcoal or wood-fired grill is controlled by regulating
airflow with the cooking region, by controlling the amount of
convection heat and/or radiant energy from the firebox that reaches
the cooking region, or by a combination of such regulating and
controlling. Similar to prior systems, air circulation in the
cooking region can also be maintained to evenly disperse heat
within the cooking region. Regulating airflow by supplying ambient
air to and exhausting air from the cooking region may be performed
with the aid of blowers, or simply by opening and closing vents
according to a temperature setting. Controlling the amount of
radiant energy or convection heat reaching the cooking region is
generally achieved by providing a variable mechanical shutter that
varies the exposure of firebox energy to the cooking region or by
increasing fuel oxidation using a charcoal blower fan. In addition,
the regulating and/or controlling may be achieved electronically,
i.e., under microprocessor control, or mechanically by, for
example, a thermal sensor such as a bimetallic element. Although
illustrated with a vertical hearth barbecue grill, aspects of the
invention may be deployed in a conventional barbecue grill where
the coals are placed horizontally.
[0017] FIG. 1 shows a vertical hearth barbecue grill 10 where
deployment of the invention is particularly suited. Grill 10 has a
housing generally formed by a base 18, a dome or lid 16, and
sidewalls 14 (only one indicated). The exemplary grill is supported
by sidebars 11 (only one indicated) as well as leg extensions 12
and 13. A generally vertically disposed firebox hearth 20 inside
the grill 10, which is preferably backwardly inclined, supplies
radiant and convection heat to a cooking region 30 in front of the
firebox hearth 20 and enclosed by a cover 22 (also depicted in FIG.
2). Cover 22 substantially forms an enclosure with the grill
housing by mating with the sidewalls 14 and base 18. Multiple
cooking grids 24, 26, and 28 support foodstuff within cooking
region 30. In a conventional horizontal barbecue grill, cooking
region 30 generally lies above a firebox chamber located near the
bottom of a base, and a dome or lid mates with the base to form an
enclosure.
[0018] In accordance with an aspect of the invention, cooking
temperature within region 30 is adequately regulated or controlled
according to the output of a temperature sensor or detector despite
uncontrollable burn rates of charcoal or wood fuels. A first
embodiment shown in FIGS. 2A and 2B includes one or more exhaust or
vent fans 32 and 34 controlled by a processor module 36 in
accordance with an output signal of a sensor or detector 42 exposed
to cooking region 30. Fans 32 and 34 establish an ambient air path
in communication with cooking region 30, and preferably comprise
readily available microprocessor cooling fans or the like that are
adapted to withstand temperatures on the order 200-300.degree. C.
or more. Any number of commercially available cooling fans may be
used, and such fans may be arranged in push-pull arrangement where
one sidewall 14 intakes ambient air and the opposed sidewall
exhausts air from region 30. Alternatively, air intakes and exhaust
ports of the cooking region 30 may be respectively located at upper
and lower positions of a single sidewall 14 in order to displace
hot air inside the cooking region 30 with cooler ambient air
external of region 30. Because the substantially enclosed cooking
region 30 of vertical barbecue grill 10 is not airtight, fans 34
and 34 need only exhaust or supply air to effectively establish air
flow with the ambient environment in order to maintain a
temperature setpoint. As earlier indicated, internal circulation to
maintain even temperature dispersion can be achieve in a manner
similar to prior systems, i.e., disposing a circulatory fan inside
the region 30.
[0019] FIGS. 3A and 3B show one form of a microprocessor module 36
that provides electronic temperature control within cooking region
30. Module 36 includes, among other things, a microprocessor 40,
boot ROM 27, a probe 42 supported on base 43, an optional tone
generator or speaker 46, a thermostat 47, an series of LEDs 48
(optional) to visually indicate a pre-designated condition, and a
thermoelectric converter 44 all of which may be mounted on a
printed circuit (PC) board and encased in a module casing attached
to sidewall 14. The PC board may further include analog-to-digital
and digital-to-analog and other circuitry embedded within an
integrated circuit 29, which may be needed to perform sampling and
control functions. Preferably, module 36 attaches to sidewall 14,
which has a window that enables exposure of a power converter 44
directly to the heated cooking region, or the exposure of converter
44 directly to a radiant energy path of firebox hearth 20 in order
to effectively convert waste heat to electrical power. Probe 42 is
a sensor or detector that may protrude through sidewall 14 into the
area of the cooking region 30, and that provides an input to
microprocessor 40. Sensor 42 may comprise a thermocouple,
bimetallic element, heat sensor, IR (infrared) sensor, or other
device known in the art to detect or sense heat or radiant energy.
Instead of being probe-like, sensor 42 may have a low profile that
substantially parallels the inner surface of sidewall 14.
[0020] Thermoelectric converter 44 is a semiconductor device that
converts heat or radiant energy to electrical electricity for
supplying power to microprocessor 40, as well as to power other
elements, e.g., the fans, speaker, and LEDs of the module 36. Such
thermoelectric converters are commercially available from Hi-Z
Technology, Inc. of San Diego, Calif. Converter 44 powers
exhaust-intake fans 32 and 34 via supply line 37, as well as an
optional, internal circulatory fans to maintain even temperature
dispersion inside region 30. In a preferred arrangement, the
electrical path of converter 44 and the fans share a common chassis
ground established by conductive surfaces of module 36 and sidewall
14, which are in electrical communication with each other. The
source of power may also be derived from a steam-driven mechanism,
such as disclosed in U.S. Pat. No. 5,832,811 issued Nov. 10, 1998
to King, which describes a water rotisserie
[0021] Because temperature control tasks are relatively simple, an
eight-bit machine-coded microprocessor 40, such as an Intel 8086
series processor, will suffice to effect sampling of outputs of
probe 42, converting that output to a temperature signal, comparing
the temperature signal with a setting of thermostat 47, and to
turning off and on power to fans 32 and 34 to control or otherwise
maintain a constant temperature within cooking region 30 in
accordance with a setpoint established by thermostat 47. Executable
instructions for carrying out these tasks can be stored in boot ROM
27. Instead of controlling air circulation within and/or with the
ambient environment, microprocessor 40 may control a mechanical arm
to regulate the amount of radiant energy or convection heat
emanating from the firebox hearth 20 as further described in
connection with a description of FIG. 7. In addition, rather than
controlling airflow within and without cooking region 30,
microprocessor 40 may regulate forced air draft supplied directly
to the firebox hearth 20 to control bum rate, and consequently, the
heat output of the charcoal briquettes or other fuel. Structure to
achieve this latter feature entails redirecting airflow, e.g., by
using deflecting baffles on blower fans disposed on a sidewall 14,
directly upon the fuel source in firebox hearth 20.
[0022] An audio annunciator or tone generator 46 may be
preprogrammed to audibly indicate a condition, such as successful
boot-up of microprocessor 40 or the attainment of a desired
temperature inside the cooking region 30. Microprocessor 40 may
also be programmed to excite LEDs 48 to indicate these or other
desired conditions. The number of LEDs 48 fired may, for example,
vary according to level of the internal cooking temperature where a
low temperature in region 30 is indicated by a fewer number of
fired LEDs and a high temperature is indicated by a higher number
of LEDs.
[0023] FIG. 4, where like reference numerals depict like elements
of FIGS. 3A and 3B, is a functional block diagram of a circuit to
implement the temperature control functions according to a
preferred embodiment of the present invention. In FIG. 4, power
converter 44 powers microprocessor 40. During initial firing up of
the grill, power output of converter 44 gradually increases in
accordance with thermal output of the coals or other fuel until
reaching a threshold operating temperature, at which time
microprocessor 40 successfully boots up and performs
self-diagnostics. This is typically indicated by an audio beep
signal sent by processor 40 to the audio annunciator 46. LEDs may
also ignite or flash upon boot up when sufficient power is
available to power the fans 32, 34, 33, 38.
[0024] After boot up, microprocessor automatically monitors the
output of sensor 42 to convert the information to a form useful for
comparison with an output or setpoint of thermostat 47. Thermostat
47 is adjusted or set by the user according to a desired cooking
temperature to be maintained in cooking region 30, e.g., "high,"
"medium," or "low." Temperature settings of thermostat 47 may also
range between specific temperatures in degrees Celsius (typically
100-250 degrees) and/or Fahrenheit (typically 300-700 degrees).
Also, calibration is typically performed before shipment of the
grill to the end user so that he or she need not deal with
obtaining accurate control.
[0025] During an initial stage of operation between say,
immediately after boot up, microprocessor 40 activates switch 31 to
turn on a charcoal blower fan 33. This expedites initial ignition
of the charcoal or other fuel in firebox hearth 20 as fresh air is
directed directly upon the fuel source. Due to the extreme heat of
the firebox hearth 20 when fully fired, a preferred blower
structure includes ducting ambient air using a fan from a
relatively cooler location of the grill 10, i.e., the sidewall 14,
directly to the face of the firebox. Upon reaching a second
threshold temperature, charcoal blower 33 may cease operation
whereupon microprocessor 40 trips an optional switch 42 to activate
optional internal circulatory fans 38. This is designed to maintain
even temperature distribution within the cooking region. At any
time during these operations, processor 40 begins to monitor the
output of sensor 42 and to implement a routine to compare a
representative output of sensor 42 with an output of thermostat 47,
as indicated earlier. At a condition where the temperature
represented by the output of sensor 42 exceeds the temperature
represented by the setting of thermostat 47, microprocessor 40
triggers switch 37 to activate vent fans 32, 34 in order to
displace air inside the cooking region 30 with cooler, ambient air.
When the internal cooking temperature drops, microprocessor 40
toggles switch 39 to turn off power to fans 32, 34, however,
internal circulatory fans 38 maintain their operation to keep even
temperature in the cooking region 30.
[0026] Generally, with a vertical hearth grill, excess heat is
constantly available due to the efficient, study, and hotter burn
rates of the coals or other fuel. Exhausting hot air or injecting
cooler air is a primary method of achieving temperature control.
When the firebox hearth 20 reaches near fuel exhaustion, however,
heat and radiant energy output diminishes. To recover additional
heat from available fuel remaining in the firebox hearth 20,
microprocessor 40 may again activate charcoal blower fan 33 by
firing transistor 31. This helps the remaining fuel to burn hotter,
i.e., output more heat, whereupon microprocessor 40 again performs
its feedback control function in accordance with a comparison
between the outputs of sensor 42 and thermostat 47. The foregoing
sequence continues to keep the temperature in region 30 adjusted to
the level established by the setpoint of thermostat 47. Attainment
or passage of each stage may be evidenced by firing any one or a
number of LEDs 48, or by issuing an annunciating command to audio
output 46. As indicated above, the invention includes a barbecue
grill implementing any one of the control features, taken alone or
in combination. Switches 31, 41, and 39 preferably comprise power
transistor switches.
[0027] FIG. 5 is a flow chart illustrating one method of carrying
out an aspect of the invention. A preferred method of controlling
cooking temperature in region 30 of a charcoal barbecue grill
having a charcoal-fired chamber and a cooking region defined by
substantially enclosing the cooking region and charcoal-fired
chamber within the housing comprises sensing the temperature of the
cooking region or energy radiated from the charcoal-fired chamber;
deriving power from the charcoal-fired chamber; and using power
derived from the charcoal-fired chamber to control the amount of
heat of the cooking region by producing a flow of air communicating
with at least one of the cooking region and the charcoal-fired
chamber according to a preset temperature. After initial boot up of
processor 40, as indicated in step 50, a routine executed by the
microprocessor 40 decides in step 52 whether the system resides in
a cold start state. If affirmative, the method optionally includes
turning on charcoal blower fan 33 as indicated in step 54 and then
looping at state 56 until a threshold temperature has been reached.
Looping frequency here and elsewhere in the illustrated methods is
selected according to the desired response time, and may range from
fractions of a second (or millisecond) to several minutes. The
threshold temperature is the minimum temperature, say 180.degree.
C., to assure reliable power output from converter 44 to operate
sensors, fans, and other resources.
[0028] After reaching a threshold temperature, the method includes
turning off blower fan 33 at step 58 and then entering an
operational state that monitors and regulates temperature in
cooking region 30. A first process in this operational state
includes testing at step 60 whether the internal temperature of
cooking region 30 is greater than a setpoint temperature
established by thermostat 47. If affirmative, blower fan 33 is
turned off and vent fans 32, 34 are turned on at step 62.
Thereafter, the method includes looping at step 60 to continue
testing the specified condition. When the internal operational
temperature of cooking region is not greater than the setpoint
temperature, the method includes testing at step 64 whether the
internal temperature of cooking region 20 is lower that the
setpoint temperature. If negative, the method includes looping back
to the test condition of step 60. On the other hand, if the cooking
region temperature is lower than the setpoint temperature, the
method includes turning off the vent fans 32, 24 at step 66 and
then turning on the blower fan 33 at step 68. Turning on blower fan
33 supplies fresh oxygen to the firebox hearth 20, thereby
increasing the burn rate of the fuel, which, in turn, increases
temperature in cooking region 30. The method includes continuing to
loop among the test condition of steps 60, 60, 66, and 68 until
another condition is met, e.g., the internal temperature again
rises above the setpoint temperature, in which case the routine
branches to step 62 to turn off the blower fan 33, and to turn on
vent fans 32, 34.
[0029] Instead of providing control of temperature by
energizing/de-energizing cooling/venting fans, FIG. 6 illustrates a
method of controlling internal temperature of cooking region 30 by
controlling an incrementally adjustable mechanical shutter that
alters the amount of convection heat or radiant energy from the
firebox that reaches the cooking region. In FIG. 6, after processor
40 boots up and adequate power is being generated at step 70, the
method includes testing whether the internal temperature of cooking
region 30 lies above or below a desired set point. Like the method
illustrated by FIG. 5, the "mechanical" method of FIG. 6 also
includes testing at step 72 whether the temperature in cooking
region 30 is lower or higher than a setpoint temperature
established by thermostat 47. If affirmative, the method includes
closing (e.g., an incremental reduction in the exposure window) at
step 74 a variable shutter, which operates similar to a venetian
blind, to restrict exposure of radiant energy and/or convention
heat from the firebox that reach the cooking region, and then, the
process loops back to continue testing at step 72. If during
testing at step 72 it is determined that the operating temperature
of cooking region 30 is not greater that the setpoint temperature,
the process at step 76 is executed to determine whether the set
point temperature is lower. If negative, microprocessor 40 again
loops back to step 72, and the process is again repeated. On the
other hand, if the operating temperature is lower than the setpoint
temperature, the mechanically variable shutter is adjusted
preferably by opening the mechanical vanes or slitted windows, one
increment at a time, until temperature equilibrium is ultimately
reached.
[0030] FIG. 7 illustrates a control method and apparatus for
controlling the amount of radiant energy or convection heat
reaching cooking region 30. Firebox hearth 20 containing oxidizing
fuel emits radiant energy and convention heat from a facing surface
thereof Such radiant energy and convection heat are supplied to
cooking region 30 through an incrementally adjustable mechanical
shutter assembly located between the firebox hearth 20 and cooking
region 30. FIG. 7 shows the shutter assembly spaced away from
firebox hearth 20, but in practice, the shutter assembly may be
located contiguous to the firebox hearth up to a distance of about
one to two centimeters from the face of firebox hearth 20. As
illustrated, the shutter assembly comprises panels 80 and 82, each
having a series of respective slits or windows 81 and 83 that pass
infrared rays, radiant energy, or convention heat from the firebox
hearth 20 to the cooking region 30 when aligned with each other.
The extent of exposure or the amount of energy allowed to reach
cooking region 30 is control by varying the degree of alignment by
sliding panel 80 relative to panel 82 in the direction indicated by
arrow 85.
[0031] One way to achieve alignment control, and thus temperature
control, is to provide a temperature responsive element, such as
bimetallic element 86 that responds (flexes in the direction of
arrow 91) to the temperature in cooking region 30 to increase
exposure, i.e., increasing alignment or registration of shutter
windows of panels 80, 82 in order to cause an increase in
temperature when the temperature inside cooking region is below a
setpoint, and to decrease exposure, i.e., by increasing
misalignment of shutter windows 81, 83 in panels 80, 82 in order to
cause a decrease in temperature when the temperature inside cooking
region is above a setpoint. To move the respective panels 80 and 82
into and out of alignment, bimetallic element 86 engages an
endpoint 87 of cantilevered arm 88 to move it in a direction
indicated by arrow 93. Arm 88 pivots about axis 89 to thus apply a
force to panel 82 at an opposite end point 90. A linkage 91
interconnects the arm 88 and panel 82. Adjusting the horizontal
position of the base 92 of bimetallic element 86 in a direction
indicated by arrow 94 sets an equilibrium point. The position of
base 92 is preferably adjusted or calibrated at the factory before
shipment. Also, the bi-metallic element may be positioned in the
cooking region 30, or between the firebox hearth 20 and shutter
assemble 80, 82.
[0032] The mechanical shutter may have various forms and structure,
the invention not being limited to the structure shown. For
example, a "venation blind" or rotary slit-window exposure or other
structure may also be used. Also, the temperature-responsive
element may have other structures or forms and a bimetallic element
may be replaced or substituted with other devices, as known in the
art. The shutter assembly may also be arranged as part of cover 22,
to drop down in front of the firebox hearth 20. Instead of being
controlled by a temperature-responsive element, the shutter
assembly may be controlled by an actuator that is controlled by a
microprocessor, in much the same way as the various fans are
controlled.
[0033] Instead of using the side panel 14 as a host structure, FIG.
8 shows a cover 22 that hosts the module 36, fan 32, and indicator
48 (in the form of a temperature gauge instead of a series of
LEDs). Other elements are omitted for the sake of simplicity in
illustration, it being understood that location of elements of
module 36 is a matter of design choice. Indeed, the module 36 and
associated elements may be deployed in the cover or housing of a
conventional horizontal barbecue grill. The number of individual
components may be altered and their positioning may be arranged to
accommodate the structure of the grill in the invention is
implemented. As stated above, although a vertical heart barbecue
grill is illustrated and described, embodiments of the invention
have applicability in conventional horizontal type barbecue
grills.
[0034] Accordingly, the invention is not limited to the embodiment
shown and described but encompasses variations and adaptations as
may come to those skilled in the art.
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